Controls for refrigeration systems having air cooled condensers



Dec. 3, 1963 R. s. STEWART 3,112,620

CONTROLS FOR REFRIGERATION SYSTEMS HAVING AIR COOLED CONDENSERS FiledMarch 29. 1962 TO CONDITIONED SPACE l'aavezzi'oa' Roaerfi aswvaaw,

flfiovazey United States Patent 3,112,620 CQNTRSLS F012 REFRTGERATIQNSYSTEMS HAVENG Am CGGLED QONDENSERS Robert S. Stewart, Staunton, Va,assignor to Westinghouse Electric (Iorperation, East Pittsburgh, Pa, acorporation of Pennsylvania Filed Mar. 29, 1952, Ser. No. 183,490 4Claims. or. 62-183) This invention relates to controls for refrigerationand air conditioning systems using air cooled condensers.

Due to lack of sufiicient water in many locations to cool the condensersof refrigeration and air conditioning systems, and due to the cost ofwater cooling such condensers in those locations where sufiicient wateris available, air cooled condensers are widely used. At low outdoortemperatures, the condensing pressure often is too low for there to besufiicient pressure across the expansion devices to operate themproperly.

This invention uses three fans to move outdoor air over an air cooledcondenser and in response to a predetermined, low temperature turns ofifone fan so as to decrease the cooling of the condenser and therebyincrease the condensing pressure, and in response to a predetermined lowoutdoor temperature turns off the other two fans. A single, two-stepthermostat and two relays are used to control the three fans so that onefan, two fans or three fans operate depending upon outdoor temperature.

An object of this invention is to vary the cooling of an air cooledcondenser in steps in response to variations in outdoor temperature.

Another object of this invention is to control three fans for cooling anair cooled condenser in response to outdoor temperatures so that onefan, two fans or three fans Wlll operate depending upon outdoortemperatures.

This invention will now be described with reference to the annexeddrawings, of which:

FIG. 1 is a diagrammatic view or" an air conditioning system embodyingthis invention, including an end view, in section, of a compartmentcontaining two refrigerant compressors, two air-cooled condensersconnected to the compressors, and cooled through the movement of outdoorair by three fans, one of which is shown by FIG. 1, and

2 is a side section of the condenser compartment of FIG. 1, with anupper portion of one of the condenser coils removed to show the threefans and their motors, and shows the control circuits of the fans. FIG.2 also shows one of the compressors, and the lower portion of a pipeconnecting that compressor to one of the evaporator coils of FIG. 1.

The air conditioning system illustrated has two evaporator coils it) and11 used for cooling air moved by fans 12 and 13 respectively. Theevaporator coil is connected by tubing 15 to the suction side ofrefrigerant compressor 16, the discharge side of which is connected tothe inlet end of condenser coil 17, the outlet side of which isconnected by capillary tube 18 to the coil 10. The evaporator coil 11 isconnected by tubing 25) to the suction side of refrigerant compressor21, the discharge side of which is connected to the inlet end ofcondenser coil 22, the outlet end of which is connected by capillarytube 23 to the coil 11. The capillary tubes 18 and 23 serve to expandliquid refrigerant from the condenser coils 17 and 22 respectively, intothe evaporator coils 1i and 11 respectively.

The condenser coils 17 and 22 are arranged on the legs of a V within acompartment 39 having air inlets 31 in its ends, and having air outlets32, 33, and 34 in its top. The compressors 16 and 21 are on the floor ofthe compartment 36 between the inlets 31 and the bottoms of the coils 17and 22.

A fan 36 driven by electric motor 37 is supported below the outlet 32. Asecond fan 38 driven by electric motor 3? is supported below the outlet33. A third fan 40 driven by electric motor 41 is supported below theoutlet 34. A partition 45 extends vertically between the fans 40 and 38.The fans are operated to draw outdoor air into the compartment 36through the inlets 31 over the condenser coils 17 and 22 and to blow theair from the compartment through the outlets 32, 33 and 34.

A two-step, outdoor thermostatic means 50 opens switch 51 at apredetermined low outdoor temperature, and closes switch 53 and opensswitch 52 at a predetermined outdoor temperature lower than thetemperature at which the switch 51 is opened. The switch 51 is connectedin series with control relay R1 and the electric supply lines L1 and L2.The switch S2 is connected in series with relay R2 and the electricsupply lines L1 and L2. The switch 53 is connected across the switch 51.

The relay R1 has a switch 55 connected by wires 57, 58 and 59 in serieswith the fan motor 41 and the supply lines L1 and L2. The fan motors 37and 39 are connected in parallel. The relay R2 has a switch 56 connectedby wires 64} and 61 in series with the motors 37 and 39 and the electricsupply lines L1 and L2.

Operation In operation, at outdoor temperatures high enough for thepressures across the capillary tubes 18 and 23 to be sufiicient orproper operation, the switches 51 and 52 are closed, energizing therelays R1 and R2, the switches 55 and 5a of which energize the three fanmotors to operate the three fans. Upon a predetermined reduction inoutdoor temperature, the switch 51 opens, deenergizing the relay R1which opens its switch 55, deenergizing the fan motor 41 and turning offthe fan 40 so that only the two fans 36 and 38 remain in operation. Thedecreased cooling of the condenser coils by the turning off of the fan40 causes the condensing pressure to rise sufficiently for proporexpansion in the evaporator coils.

If the outdoor temperature falls to a predetermined temperature belowthe temperature at which the switch 51 opens, the switch 52'opens andthe switch 53 closes. The opening of the switch 52 deenergizes the relayR2 which opens its switch 56 and deenergizes the fan motors 37 and 39,turning ofi the fans 36 and 38 respectively. The closing of the switch53 connected in parallel with the switch 51 turns relay R1 and the fanmotor 41 and its fan 49 back on so that there is one fan in operation.

The partition 45 prevents leakage through the inactive fan or fans.

The two compressors 16 and 21 would be controlled by a two-step indoorthermostat which is not shown.

By placing the condenser coils 17 and 22 on the legs of a V, and byusing common fans for moving outdoor air over both condenser coils,space and expense are saved.

What is claimed is:

-1. In a refrigeration system, a compartment having an outdoor air inletopening and an outdoor air outlet opening, a heat exchange coil withinsaid compartment between said openings, a partition extending across theinterior of said compartment between said openings, said coil extendingthrough said partition, a first fan within said compartment on one sideof said partition, a first motor within said compartment for drivingsaid fan, second and third, spaced-apart fans Within said compartment onthe other side of said partition second and third motors within saidcompartment for driving said second and third fans respectively, saidfans being arranged to draw outdoor air through said inlet opening andto move the said first switch, when closed, for energizing said firstmotor, a second switch closed and a third switch opened by saidthermostatic means when the outdoor tern, erature is at or above asecond predetermined temperature lower than said first temperature, saidsecond switch being opened and said third switch being closed when theoutdoor temperature falls below said second temperature, meansincludinsg'said second switch, when closed, for energizing said secondand-third motors, and means connecting said third switch across saidfirst switch so that when said thirdswitch is closed, said first motoris energized by said means included with said first switch.

2. ihe invention claimed in claim 1 in which said means includedwithsaid first switch comprises a first relay which is energized whensaid first switchis closed and a switch closed by said relay when saidrelay is energized, and in which said means included with said secondswitch comprises a second relay which is energized and a switch closedby said second relay when said second relay is energized.

3. in a refrigeration system, a rectangulm compartment having outdoorair inlet openings in its opposite sides, and having first, second andthird, aligned, spaced-apart outlet openings in its top, a partitionextending across the interior of said compartment'betweensaid first andsecond outlet openings, a pair of slanted, spaced-apart, heat exchangecoils located on the legs of a 'V-shaped' outline below said outletopenings, said coils extending through said partition, first, second andthird=fans between the tops of said coils below and in alignment withsaid first, second and third outlet openings respectiyely, a first motorWithin said compartment for drivingsaid first fan, second and thirdmotors within said compartment for driving said second and third tansrespectively, said fans being arranged to draw outdoor air through said:inlet openings and to moye the outdoor air over said coils and out saidoutlet openings, thermostatic means responsive to outdoor temperatures,a first switch closed by said means when the outdoor temperature is ator above a first redetermined temperature and opened by said means whenthe outdoor temperature falls below said first temperature, meansincluding said first switch, when closed, for energizing said firstmotor, a second switch closed and a third sw opened 0 said thermostaticneans when the outdoor temperature is ator'ahoyea second predeterminedtemperature lower than said first temperature, said second switch beingopened and'said third switch being closed when the outdoor temperaturefalls below said second temperature, means inciuding said second switch,when closed, for energizing said second and third motors, and meansconnecting-said third switch across said first switch so that when saidthird switch is ciosed, said first motor is energized by said meansincluded with said first switch.

4. The invention claimed in ciaim 3 in which said means included withsaid first switch comprises a first relay which is energized when saidfirst swtich is closed and a switch closed by said rclay when said relayis energized, and in which said means included with said second switchcomprises a second relay and a switch closed by said second relay whensaid second relay is energized.

References tCited in the file of this patent UNITED STATES PATENTS

1. IN A REFRIGERATION SYSTEM, A COMPARTMENT HAVING AN OUTDOOR AIR INLETOPENING AND AN OUTDOOR AIR OUTLET OPENING, A HEAT EXCHANGE COIL WITHINSAID COMPARTMENT BETWEEN SAID OPENINGS, A PARTITION EXTENDING ACROSS THEINTERIOR OF SAID COMPARTMENT BETWEEN SAID OPENINGS, SAID COIL EXTENDINGTHROUGH SAID PARTITION, A FIRST FAN WITHIN SAID COMPARTMENT ON ONE SIDEOF SAID PARTITION, A FIRST MOTOR WITHIN SAID COMPARTMENT FOR DRIVINGSAID FAN, SECOND AND THIRD, SPACED-APART FANS WITHIN SAID COMPARTMENT ONTHE OTHER SIDE OF SAID PARTITION SECOND AND THIRD MOTORS WITHIN SAIDCOMPARTMENT FOR DRIVING SAID SECOND AND THIRD FANS RESPECTIVELY, SAIDFANS BEING ARRANGED TO DRAW OUTDOOR AIR THROUGH SAID INLET OPENING ANDTO MOVE THE OUTDOOR AIR OVER SAID COIL AND OUT SAID OUTLET OPENING,THERMOSTATIC MEANS RESPONSIVE TO OUTDOOR TEMPERATURES, A FIRST SWITCHCLOSED BY SAID MEANS WHEN THE OUTDOOR TEMPERATURE IS AT OR ABOVE A FIRSTPREDETERMINED TEMPERATURE AND OPENED BY SAID MEANS WHEN THE OUTDOORTEMPERATURE FALLS BELOW SAID FIRST TEMPERATURE, MEANS INCLUDING SAIDFIRST SWITCH, WHEN CLOSED, FOR ENERGIZING SAID FIRST MOTOR, A SECONDSWITCH CLOSED AND A THIRD SWITCH OPENED BY SAID THERMOSTATIC MEANS WHENTHE OUTDOOR TEMPERATURE IS AT OR ABOVE A SECOND PREDETERMINEDTEMPERATURE LOWER THAN SAID FIRST TEMPERATURE, SAID SECOND SWITCH BEINGOPENED AND SAID THIRD SWITCH BEING CLOSED WHEN THE OUTDOOR TEMPERATUREFALLS BELOW SAID SECOND TEMPERATURE, MEANS INCLUDING SAID SECOND SWITCH,WHEN CLOSED, FOR ENERGIZING SAID SECOND AND THIRD MOTORS, AND MEANSCONNECTING SAID THIRD SWITCH ACROSS SAID FIRST SWITCH SO THAT WHEN SAIDTHIRD SWITCH IS CLOSED, SAID FIRST MOTOR IS ENERGIZED BY SAID MEANSINCLUDED WITH SAID FIRST SWITCH.